Auth bypass in Cyberlord92 Saml Single Sign On – Sso Login

CVE-2026-15981

The SAML Single Sign On – SSO Login plugin for WordPress is vulnerable to Authentication Bypass in all versions up to, and including, 5.4.4. This is due to the mo_saml_validate_signature() function performing a loose boolean check on the raw tri-state integer returned by PHP's openssl_verify(), causing an error return value of -1 to be evaluated as truthy and therefore treated as a successful signature verification. This makes it possible for unauthenticated attackers to log in as any existing WordPress user, including administrators, by submitting a crafted SAMLResponse containing an attacker-controlled NameID and a deliberately malformed signature value that triggers an OpenSSL processing error — bypassing verification entirely and resulting in wp_set_auth_cookie() being called for the targeted account.

Vulnerability class: Broken Authentication

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.024 (83.7th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 83.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-15981: held from 0.019 to 0.024.

EPSS over last 30 days · oldest: 0.019 · newest: 0.024 · change: +0.005

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-15981?
CVE-2026-15981 is a critical-severity vulnerability in Cyberlord92 Saml Single Sign On – Sso Login, classified under Improper Authentication. CVSS score: 9.8/10. Published 2026-07-23.
How severe is CVE-2026-15981?
Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2026-15981 known to be exploited?
2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.